1. Field of the Invention
The present invention generally concerns methods and devices for the construction upon the surface of the earth of cast in-situ concrete footings which footings serve as support for subsequently built foundation walls, and the like.
The present invention particularly concerns fixtures that efficiently define the top surfaces and the edges of cast in-situ concrete footings, and that accurately locate cast-in-place elements which cooperate structurally with subsequently superimposed walls, which walls can be constructed from any of solid concrete, grouted building blocks of cement-masonry or foam units, shot-creted insulated panels, et cetera.
2. Description of Prior Art
2.1 General Background
Traditionally built footings for cement masonry unit (CMU) foundation walls are made of cast in-situ concrete, often having a top surface defined only by string lines and manual tooling (except in the case of basement construction, where the footing is traditionally formed with boards). Usually this footing will have resulting corners and steps which do not correspond with the desired accuracy to the pre-determined CMU modular units. Also, vertical reinforcing stub-ups are frequently misplaced. Thus, a lot of time is wasted in the construction of the subsequent CMU wall in dealing with these irregularities.
Experienced tradesmen will frequently set the first course of block while the concrete of the footing is still wet, thus verifying block modular layout, et cetera, before the footing concrete has set. Unfortunately many situations do not easily permit use of this method, such as where sloping sites require many steps in the footing, or where pre-situated (before footing concrete placement) vertical reinforcing steel (rebar) is required by building (seismic) codes. With the vertical rebars pre-located, the presence of the pre-location fixtures, as well as the rebars themselves, cause difficulty in placing the block onto wet footing concrete, regardless of any presence of steps, eat cetera.
Where fixtures must be erected to locate pre-situated vertical reinforcing steel, much labor is consumed in situating the fixture and in laying out the vertical rebars. Most building jurisdictions in seismically active areas require that these Laborious steps be taken, despite the resistance from the building trades, because it is the only way to be sure that the foundation wall reinforcing will be placed properly, and where it is most needed.
Foam building-block products are generally set on formed footings of cured concrete, and this concrete does not necessarily have a trued top surface. The light weight of the foam causes a buoyant effect as grout is placed. Because of these factors, a sacrificial 2.times.4 wood keeper is usually (powder-actuated) nailed to the footing concrete on either side of the first course of foam block, in order to prevent (otherwise frequent) grout blow-outs at the bottom of the foam block build-up.
Thus to such extent as foam block methods are used for construction of basements, the layout of foundation walls (in the horizontal plane) is undertaken three times in three distinct operations. First, foundation layout is undertaken in setting the footing forms. Second, foundation layout is undertaken more accurately locating block modules for vertical reinforcing and turning point placement, etc. And third, foundation layout is undertaken in setting the 2.times.4 keepers at either side of the blocks.
Other proprietary in-situ concrete wall construction methods use welded wire mesh panels (WWMP), which typically incorporate built-in foam insulation panels. The panels are set in place contiguously and are typically covered with in-situ concrete via pneumatic methods (shotcrete), or else with conventional concrete and wall forms. The WWMP panel walls usually have thin "wythes" of concrete requiring very accurate placement of an increased number of footing vertical rebars. Many difficulties result in placement of WWMP's. Code-required concrete cover over reinforcing steel can not be achieved if these vertical stub-ups are not very accurately placed. Carefully built fixtures for this purpose are essential.
2.2 Specific Prior Art
The most relevant prior art relating to this and related co-pending applications is believed to be that disclosed in U.S. Pat. No. 3,397,494 to Waring, issued Aug. 20, 1968. In the method of Waring a perimeter member is supported in place by machine-threaded rods in order to form a special recessed ledge about a concrete slab (for a proprietary wall system). These rods thread into bearing pads that sit upon the earth, and then provide vertical adjustment to the perimeter member. No allowance is provided for rod location. It must be directly at a member (normal bolt-sized) hole, regardless of what local anomaly or rock might be at that location.
The amount of buoyant force which would be generated by properly placing concrete against the underside of the perimeter section shown does not appear to be addressed by the Waring support method. The Waring rod supports offer little resistance to uplift because they are of normal machine thread, which is too fine and slight to have a capability of effectively threading into the earth for anchorage.
Horizontal adjustment and lateral stability are not accomplished by the Waring Method, and so a substantial redundant perimeter forming method of wood members is shown to be necessary with these adjustable vertical support methods.
2.3 Objectives
Accordingly, it would be useful if some method for the construction of poured concrete footers could really serve as a starting point for the construction of walls, directly above the earth, with a minimum of effort.
The method would desirably permit easy and accurate pre-location of any structural elements necessary for the construction of the wall, all with a minimum of skill.
Modular increments specific to a given construction module would desirably be pre-located--where such increments must be known for steps and turns in the wall--with a minimum of effort and skill.
Low-cost rigid-element fixtures would desirably force all the planes of construction, all reinforcing elements, all steps, and all turns into the proper locations for diverse specific wall construction methods.